Ionics最新文献

Bismuth microspheres@N-doped porous carbon anode (Bi@NPC-2) is rational designed and successfully prepared by an easy one-pot heat treatment process. The composite demonstrated superior sodium storage performance, including excellent cyclic stability of 326.4 mAh g⁻¹ after 4000 cycles at 5 A g⁻¹ with a capacity retention of 95% and ultra-high rate capability of 286.7 mAh g⁻¹ at a high current rate of 40 A g⁻¹. This excellent performance is mainly due to the unique material design, the three-dimensional porous structure not only helps to mitigate the volume expansion of bismuth, but also shortens the diffusion path of sodium ions. In addition, nitrogen doping improves the conductivity of the electrode and provides more active sites for sodium storage. More importantly, the preparation process is simple, and the raw materials used are cheap, thus the Bismuth microspheres@N-doped porous carbon composite shows important practical large-scale applications. This one-step sintering method can also be applied to other alloy-based sodium storage materials.

Niobium-based phosphates have the advantages of high stability and environmental protection and have good application prospects in sodium-ion batteries. The pure phase of Na(NbO₂)₂PO₄ (NNP) powder was successfully synthesized by different methods in this work, and the materials were characterized via XRD, XPS, SEM, and electrochemical methods. At the current density of 100 mA g⁻¹, the discharge-specific capacity of NNP is 521.8 mAh g⁻¹ in the first cycle and remains at 462.4 mAh g⁻¹ after 200 cycles, indicating that it has good cycling stability. The kinetic results obtained from cyclic voltammetry (CV) show the pseudo-capacitance contribution accounts for a large percentage of the capacity. The charge transfer resistance of NNP is 260.3 Ω, which is significantly smaller than the others derived from electrochemical impedance spectroscopy (EIS). These pointed to the advantages of NNP in anode material for SIBs.

Present report explores microrod-shaped bimetallic cobalt iron phosphate grown through a cost-effective, single-run chemical route at 70 °C on stainless steel substrate. XRD, FTIR, TEM, and XPS analyses confirm the formation of the Co₃Fe₄(PO₄)₆ phase, wherein cobalt exhibits a +2 oxidation state, and iron adopts a +3 oxidation state. SEM analysis reveals the interlocking arrangement of micro-rods. Obtained surface architecture enhances structural integrity and establishes an efficient electrical channel for electron transfer which excels exceptional specific capacitance to 1643 F/g at a 5 mV/s scan rate (1208 F/g at 2.5 mA/cm²) with an impressive stability of 98% at 5000 CV cycles. These excellent outcomes spurred the fabrication of a symmetric supercapacitor, exhibiting 170 F/g specific capacitance at 5 mV/s with a 1.3 V potential window. In-depth analysis has been conducted to identify the origin of capacitive behavior, examining both surface and diffusion-controlled charge components. Through a practical demonstration, the constructed device effectively operated a 1 V DC fan, showcasing its promising practical applications.

A special core–shell structure catalyst is designed, synthesized and tested in a fuel cell by a simple process of embedding a platinum nanocrystal with an amorphous Co-B shell (Pt@Co-B), which is called “caystals@amorphous crystals (C@AC).” This new material shows excellent catalytic activity as an anode catalyst of direct borohydride fuel cells (DBFCs) with the maximum power output of 110 mW cm⁻² at 25 °C. Pt@Co-B with such highly power density, outperformed some noble metal and bimetallic catalysts which are recently reported in the literature. The cell has good durability, with no observed attenuation after 154 h. We speculate that this excellent catalytic performance can be due to the synergistic effect between amorphous shell and crystalline core.

Graphical Abstract

Widespread commercialization of sodium-ion batteries (SIB) is limited by the shortcomings of existing electrode materials, so the search and testing of various sodium compounds suitable for SIB are relevant. This paper presents the results of a study of the sodium diffusion mechanisms in quasi-layered oxides Na_1-xV_1-xMo_1+xO₆, which are potentially promising for applications for SIB. A simple synthesis procedure has been developed, which makes it possible to obtain compounds in a wide range of compositions up to x = 0.2. To elucidate the mechanisms of sodium diffusion, we applied a comprehensive approach that combines material characterization at the “macro” (XRD, impedance spectroscopy) and “atomic-scale” levels (NMR, ab-initio calculations). Our results reveal rather fast sodium dynamics: Ionic conductivity reaches the values of 10^–3 S/cm at T > 730 K. It has been found moreover that the diffusion mechanism changes with increasing temperature. At T < 625 K, sodium motion occurs mainly along the crystallographic b axis due to atomic jumps with the shortest jump length ≈ 3.6 Å and activation energy E_a ~ 1 eV. With increasing temperature, another type of jumps along a axis (in the ab plane) with a jump length of ≈ 5 Å and a barrier value of 2 eV is also activated.

Doped and undoped compositions of Ce_1-xSr_xO_2-δ (x = 0, 0.025, 0.05, 0.075, and 0.1) are synthesized using the sol–gel auto-combustion method. The calcined powders are sintered at 1450 °C for four hours (h). The sintered samples are characterized and tested by various experimental techniques to study their structural, microstructural, and electrical properties as electrolytes for intermediate-temperature solid oxide fuel cells (IT-SOFC). The X-ray diffraction results confirm the single-phase formation except for the x = 0.1 sample, which also exhibited a minor secondary phase, i.e., SrCeO₃. X-ray photoelectron spectroscopy (XPS) reveals the mixed oxidation state of cerium (Ce⁴⁺/Ce³⁺) in undoped and doped CeO_2. The presence of oxygen vacancies has also been verified using Raman spectroscopy. The Sr creates oxygen vacancies and acts as the sintering aid to densify the samples. The highest conductivity is 6.46 × 10^–3 S.cm⁻¹ for x = 0.075 sample at 600 °C. The power density of the sample is about 89 mW.cm⁻² at 600 °C. With a relative density of ~ 97%, the x = 0.075 sample can be used as a solid electrolyte in IT-SOFC.

Lithium-sulfur batteries have become a research hotspot in the field of energy storage due to their high capacity and low cost. However, lithium metal anodes' short cycle life and safety performance severely limit their commercial application. Here, we used an “in situ” method to form a stable artificial solid electrolyte interface on the surface of the metal lithium, which can control the electrochemical behavior of the interface between the lithium metal and the electrolyte and inhibit the growth of lithium dendrites. The electrochemical performance of lithium-sulfur batteries with protected lithium anode is greatly enhanced. The discharge capacity remains at 1519.6 mAhg⁻¹ after 100 cycles at 0.1 C. In addition, the rate capability of lithium-sulfur batteries is also significantly improved, delivering a reversible capacity of 685.7 mAh g⁻¹ at 0.5 C.

Ion-conducting thin nanocomposite polymer electrolyte films were prepared by solution casting technique using poly (ethylene oxide) (PEO) and sodium lauryl sulfate (NaC₁₂H₂₅SO₄) salt complexation in the ratio 30:1. Fine nanoparticles of iron(III) oxide (Fe₂O₃) were incorporated into the polymer matrix at various weight percentages. The XRD pattern exhibited the amorphous nature of the novel nanocomposite polymer electrolyte thin films, and FTIR studies showed the complexation and the incorporation of the nanoparticles in the polymer matrix. The maximum ionic conductivity of 3.76 × 10⁻⁶ Scm⁻¹ was obtained for the sample with 5 wt.% of Fe₂O₃. Thermal and morphological studies showed a reduction in the degree of crystallinity of the polymer material. The electrochemical cell was fabricated at room temperature (304 K) using the chosen best conducting thin nanocomposite polymer film with an open circuit voltage (OCV) of 1.255 V and a short circuit current (SCC) of 648 µA.